Clutch for a rotary switch drive shaft

ABSTRACT

A clutch for disconnecting a drive shaft of an electric switch from a switch actuating element which includes a rotary shaft, particularly useful for the return or trip-free release of a rotary switch, comprises a differential gearing coupled between the rotary shaft of the actuating element and the switch drive shaft. The gearing includes a first gear connected to the rotary shaft for rotation therewith, a second gear connected to the drive shaft for rotation therewith, idler gears meshing with the first and second gears and transmitting rotation from one to the other, and a housing carrying the idler gears and mounted for rotation. A releasable latch carries the idler gears and is arranged selectively to permit and stop rotation of the gearing housing.

The present invention relates to a clutch means between an actuatingelement for selectively switching an electric switch on and off, theactuating element including a rotary shaft, and a drive shaft for theswitch, the shafts being mounted coaxially. The actuating element may bea rotary knob and the clutch means is particularly useful for the returnand trip-free release of rotary switches.

Various switching arrangements are known for automatically switching offan instrument actuated by a switch or for preventing the switch frombeing switched on at the occurrence of any impediment in the circuit,such as an undesirably high or low voltage supply or a cut-off ofelectric current. Such conventional arrangements usually have toggleswitches and have the disadvantage that the rotary movement of theactuating element must be translated into a rectilinear movement of thetoggle and this must be converted back into a rotary movement of theswitch drive shaft. This multiples conversion of actuating forcesinvolves a great number of bearings, with a concomitant increase infriction. In addition, these toggle switches are useful only for certaincontact arrangements.

It is a primary object of this invention to provide a clutch of theabove-indicated type which permits connection from an actuating elementto a great variety of contact arrangements without interference with thefunctioning of the installation and while actuating multi-stage contactswhich may then be released in selected positions. The contactarrangements may vary in respect of the magnitude of the angle ofrotation of the switching shaft and the number of contacts and theirswitching programs, such as cam switches.

These and other objects and advantages are accomplished in accordancewith the invention with a differential gearing coupled between therotary shaft of the actuating element and the drive shaft. The gearingincludes a first gear means connected to the rotary shaft for rotationtherewith about the axis of the shafts, a second gear means meshing withthe first gear means and connected to the drive shaft for rotationtherewith about the axis, and a housing carrying one of the gear meansand mounted for rotation about the axis. A releasable latch means isarranged selectively to permit and stop rotation of the gearing housing.In the illustrated embodiments, the second gear means comprises idlergears meshing with the first gear means and the housing carries theidler gears.

In a preferred embodiment, an exterior housing surrounds the clutchmeans and spring means, preferably a coaxial spiral spring, is connectedbetween the gearing housing and the exterior housing, the spring meansbeing biased to press the gearing housing against the latch means toprevent rotation of the gearing housing.

At the occurrence of a release impulse signal, the contact system isbrought to the rest or zero position while the actuating element isreleased and moves into a release position totally independently of thecontact system. Holding the actuating element in the "on" position atthe occurrence of a release impulse signal does not prevent trip-freerelease of the switch. Furthermore, the return force stored in theclutch means in the zero position can release the clutch at theoccurrence of a release impulse signal only in the on position and notin the zero position of the actuating element.

The above and other objects, advantages and features of the presentinvention will become more apparent from the following detaileddescription of certain now preferred embodiments thereof, taken inconjunction with the accompanying drawing wherein

FIG. 1 is an exploded perspective view of a clutch means according toone embodiment of this invention, most of the exterior housing not beingshown;

FIG. 1a and 1b schematically illustrate switch positions;

FIG. 2 is a vertical axial section of the clutch means shown in FIG. 1;

FIG. 3. is a top plan view of the left-side portion of FIG. 1, with therotary shaft and cover of the exterior housing removed;

FIG. 4 is a similar top plan view showing the interior of the clutchmeans, with the control disc, the auxiliary plunger and the first gearmeans also removed;

FIG. 5 is a transverse section along line V--V of FIG. 2; and

FIG. 6 is a section similar to FIG. 2 of the left-side portion of theclutch means, illustrating another embodiment of the gearing.

Referring now to the drawing, wherein like reference numerals designatelike parts functioning in an equivalent manner in all figures, FIGS. 1to 5 show one embodiment of the clutch between rotary shaft 2 and switchdrive shaft 2'. In the illustrated embodiment, the coaxially mountedshafts are of polygonal cross section and an actuating knob (not shown)may be attached to rotary shaft 2 for ease of operation. Diagrams A andB, in FIGS. 1a and 1b, show the possible positions of actuating element2 and drive shaft 2', as will be explained hereinafter in thedescription of the operation of the illustrated apparatus 1.

An exterior housing 4 consists of two laterally adjacent housing partscovered by a common closure member which has an opening holding bearingring 6 for rotary shaft 2 whereby the rotary shaft is centered in onehousing part and coaxially extends thereinto. The rotary shaft passesthrough polygonal bore 12 in control disc 7 underlying bearing ring 6whereby the control disc is keyed to the rotary shaft for rotationtherewith.

A differential gearing is coupled between rotary shaft 2 and drive shaft2'. This gearing is shown to include a first gearing means consisting ofbevel gear 8 which has a coaxial polygonal bore receiving rotary shaft 2so that the shaft is keyed to the bevel gear and this gear rotates withthe rotary shaft. The gearing further includes a second gearing meansconsisting of bevel gear 9 axially spaced from bevel gear 8, coaxialwith drive shaft 2' and keyed for rotation therewith, and idler gears 11meshing with the bevel gears and interconnecting the same. The gearingalso includes housing 10 carrying idler gears 11 and mounted forrotation about the axis of the shafts and exterior housing 4. Switchdrive shaft 2' has a stop (not shown) for its zero or rest position.

Gearing housing 10 has coaxial skirt 10a extending therefrom, thehousing skirt being coaxial with the exterior housing, and spiral spring13 is arranged coaxially between skirt 10a and exterior housing 4, oneend of the spiral spring being connected to the skirt and the otherspiral spring end being connected to the exterior housing for biasinggearing housing 10 against the latch means to be described hereinafterand thus to prevent rotation of the gearing housing. The springarrangement is best shown in FIG. 5.

The releasable latch means arranged selectively to permit and stoprotation of gearing housing 10 comprises locking projection 19 on theperiphery of housing 10 and main plunger 21 slidable into and out ofengagement with the locking projection. Stop 20 is circumferentiallyspaced from projection 19 on the periphery of housing 10 (see FIG. 4),and stop 20 is free to move in an arcuate chamber recessed in the wallof exterior housing 4 so as to permit limited rotation of housing 10.Main plunger 21 has stop or nose 26 cooperating with locking projection19.

The latch means control includes control disc 7 which has stop or catch14 extending radially from its periphery and circumferentially spacedtherefrom two successive peripheral recesses 15 and 16. Stop 14 is freeto move in arcuate chamber 18 in exterior housing 4 so as to permitlimited rotation of the disc in the direction of arrow 17 (see FIG. 3).Seen in the direction of rotation, leading edge 16a of recess 16 andtrailing edge 15a of recess 15 are flattened or bevelled in relation tothe periphery of control disc 7. Auxiliary plunger 22 is slidablymounted on main plunger 21 and is spring-biased into engagement with oneof the recesses in the control disc.

The laterally adjacent part of exterior housing 4 carries guideway 24for slidable main plunger 21 which is a bolt of substantiallyrectangular cross section which may be reciprocated axially and in aradial direction with respect of gearing housing 10 along the guideway.The main plunger defines seat 25 for auxiliary plunger 22 which permitsslidable reciprocation of the auxiliary plunger axially and in a radialdirection with respect of control disc 7 along seat 25 serving as aguideway for the auxiliary plunger. The seat includes a shoulder andcoil spring 30 is mounted between the shoulder and auxiliary plunger 22for biasing the auxiliary plunger into engagement with a recess in disc7. Spring 30 is held on frusto-conical bolt 29 extending from the rearend of auxiliary plunger 22 and spring 28 is held on frusto-conical bolt27 extending from the rear end of main plunger 21. The bias of spring 30acting on the auxiliary plunger exceeds that of spring 28 acting on themain plunger.

While mechanical, hydraulic or pneumatic means may be used for operatingthe latch means, electromagnetic operating means are illustrated herein.This electromagnetic operating means comprises an electromagnetconsisting of core 40 and coil 41 cooperating with a plunger actuatingelement 23. Element 23 comprises a pair of walls 33, 34 of magneticmaterial arranged in transverse alignment with respect to main plunger21, the walls being attracted and held in position by the electromagnetupon energization thereof. Coaxially arranged bolts 38, 39 extendtransversely of the main plunger and are affixed thereto. The boltscarry rollers 36, 37 received in obliquely extending slots 34, 35 inwalls 33, 34.

The apparatus described hereinabove operates as follows:

In the illustrated zero or rest position, the electromagnet is energizedto hold walls 32, 33 down and thus keeps nose 26 of main plunger 21 inlocking engagement with projection 19 of gearing housing 10 under thebias of spring 28. This prevents the gearing housing from rotating andholds return spring 13 under tension. In this position of the switch,auxiliary plunger 22 is in its forward position to engage the recess incontrol disc 7, spring 30 being substantially free of biasing tension.

When the actuating knob is turned to rotate rotary shaft 2 clockwise inthe direction of arrow 3 (see FIG. 1a) from the zero position into theon position, the differential gear causes counterclockwise rotation ofswitch drive shaft 2' in the direction of arrow 5, see also FIG. 1b, therotation of shaft 2 being transmitted to shaft 2' by bevel gears 8 and 9respectively keyed to the shafts, and interconnecting idler gears 11.Gearing housing 10, however, is held against rotation by main plunger 21and return spring 13 remains accordingly loaded. Auxiliary plunger 22,on the other hand, is retracted against the bias of spring 30 by therotation of control disc 7 in the direction of arrow 17 (see FIG. 1)since this rotation causes recess 15 to move out of alignment with theauxiliary plunger and the succeeding peripheral portion of the controldisc forces the spring-biased auxiliary plunger rearwardly. While thespring bias on the auxiliary plunger exceeds the bias of spring 28acting on the main plunger, it is less than the sum of the force ofspring 28 and the electromagnet acting on main plunger 21. Therefore,the main plunger remains stationary and the latch means holds gearinghousing 10 against rotation. To turn the switch off, the rotation ofrotary shaft 2 is reversed, the operation being otherwise identical tothat hereinabove described.

When, in case of a circuit failure, such as a short circuit,insufficient voltage supply, etc., a protective circuit device comesinto operation and emits a release impulse signal, the electromagnet isdeenergized immediately in response to this signal, thus releasingactuating element 23 of main plunger 21. This nullifies the magneticforce acting upon the main plunger.

In this operating condition, when the knob (not shown) on rotary shaft 2is turned to rotate the shaft and control disc 7 clockwise into the onposition (FIG. 1a), switch drive shaft 2' at first moves with shaft 2but counterclockwise through a small angle of rotation, due to theoperation of the gearing between the two shafts described hereinabove.However, as soon as auxiliary plunger 22 has been depressed against thebias of spring 30 by the rotation of disc 7, the retracting movement ofthe auxiliary plunger also forces main plunger 21 to retract because thebias of spring 30 exceeds the bias of spring 28. Since no magnetic forceacts on the main plunger, it is solely subject to the spring forces, thefree backward sliding movement of the main plunger being possible due tothe oblique extension of guide slots 34, 35 for rollers 36, 37. Thus,nose 26 will be removed from locking engagement with projection 19,enabling gearing housing 10 to be rotated clockwise about its axis underthe force of return spring 13 until it has reached its zero or restposition determined by a stop (not shown). When the knob on rotary shaft2 is released, i.e. no outside turning motion is imparted thereto, itwill continue under the residual tension in spring 13 to turn clockwiseinto a release position (see FIG. 1a ) in which the spring is at rest(tensionless) and catch 14 on control disc 7 rests against a shoulder inarcuate chamber 18. Thus, the clutch means of the present inventionenables switch drive shaft 2' to be readily disconnected from actuatingelement 2 when something is wrong in the installation in which theswitch is used, the actuating knob itself automatically moving into arelease position.

After the fault in the circuitry has been repaired and the protectivecircuit no longer emits a release impulse signal, the electromagnet isautomatically re-energized. This causes actuating element 23 to bemagnetically attracted and pulled down into the position shown in FIG. 2to reengage main plunger 21 with gearing housing 10 and auxiliaryplunger 22 with control disc 7. The switch may then be operated again,i.e. shaft 2' may be turned by rotation of shaft 2, after rotary shaft 2has been turned counterclockwise against the force of return spring 13from it release position to the zero position (FIG. 1a) so that nose 26locks with projection 19 and auxiliary plunger 22 rests in recess 15. Aslong as the circuit remains in disrepair, i.e. it emits a releaseimpulse signal, rotary shaft 2 can be turned only into the zero positionbut it is not possible to turn it to the on position. As long as releaseimpulse signal remains, the latch means cannot be engaged so that, uponrelease of the rotary shaft from an outside turning force, it willautomatically turn into the release position. Thus, the switch cannot beoperated as long as the circuit has not been repaired.

Gearings equivalent to that shown in FIGS. 1 and 2, may, of course, beused in the clutch means of this invention, a planetary gearing beingshown by way of example in FIG. 6.

Since all other parts are unchanged in this embodiment, only the gearingwill be described to avoid prolixity. The illustrated planetary gearcomprises sun gear 45 keyed to rotary shaft 2 and planetary idler gears42 carried by gearing housing 44 which is functionally equivalent tohousing 10. Ring gear 43 surrounds the idler gears which mesh with gears45 and 43 to interconnect the same. Drive shaft 2' is keyed to ring gear43. Obviously, the ring gear could be keyed to shaft 2 and the sun gearto shaft 2'. The operation of this embodiment is identical to thathereinabove described.

While the invention has been described in connection with certainspecific structural embodiments, it will be understood that variationsand modification of the illustrated structures will readily occur tothose skilled in the art, particularly after benefiting from the presentteaching, without departing from the spirit and scope of this inventionas defined in the appended claims.

What is claimed is:
 1. A clutch means between an actuating element forselectively switching an electric switch on and off, the actuatingelement including a rotary shaft, and a drive shaft for the switch, theshafts being coaxially mounted, comprising1. a differential gearingcoupled between the rotary shaft of the actuating element and the driveshaft, the gearing includinga. a first bevel gear coaxial with therotary shaft and keyed thereto for rotation therewith about the axis ofthe shafts, b. a second bevel gear means axially spaced from the firstgear, coaxial with the drive shaft and keyed thereto for rotationtherewith about the axis, c. idler gear means meshing with the bevelgears and interconnecting the same, and d. a housing carrying the idlergear means and mounted for rotation about the axis,
 2. a releasablelatch means arranged selectively to permit and stop rotation of thegearing housing,
 3. an exterior housing surrounding the gearing housing,and
 4. spring means connected between the gearing housing and theexterior housing, the spring means being biased to press the gearinghousing against the latch means to prevent rotation of the gearinghousing.
 2. The clutch means of claim 1, wherein the actuating elementis a rotary knob.
 3. The clutch means of claim 1, wherein the springmeans is a spiral spring, the gearing housing, the exterior housing andthe spiral spring being coaxially arranged.
 4. The clutch means of claim1, comprising electromagnetic means for operating the latch means. 5.The clutch means of claim 1, wherein the latch means comprises a lockingprojection on the periphery of the gearing housing and a plungerslidable into and out of engagement with the locking projection forselectively permitting rotation of the gearing housing.
 6. The clutchmeans of claim 5, further comprising a latch means control, the controlincluding a control disc keyed to the rotary shaft for rotationtherewith, a stop on the periphery of the control disc for preventingfurther rotation, the periphery defining a recess circumferentiallyspaced from the stop, and an auxiliary plunger slidably mounted on theplunger and spring-biased into engagement with the recess.
 7. The clutchmeans of claim 6, wherein the first-named plunger defines a seat for theauxiliary plunger permitting slidable movement of the auxiliary plungerin respect of the first-named plunger, the seat including a shoulder,and a spring mounted between the shoulder and the auxiliary plunger forbiasing the auxiliary plunger into engagement with the recess.
 8. Theclutch means of claim 6, wherein the leading edge of the recess in thedirection of rotation of the control disc is flattened in relation tothe periphery of the disc.
 9. The clutch means of claim 6, furthercomprising a spring means for biasing the first-named plunger intoengagement with the locking projection, an electromagnet for slidinglyactuating said plunger, the spring bias on the auxiliary plungerexceeding the bias of the spring acting on the first-named plunger butbeing less than the sum of the force of the spring and electromagnetacting on the first-named plunger, and no spring bias being exerted uponthe auxiliary plunger in a rest position of the switch.
 10. A clutchmeans between an actuating element for selectively switching an electricswitch on and off, the actuating element including a rotary shaft, and adrive shaft for the switch, the shafts being coaxially mounted,comprising1. a planetary gear coupled between the rotary shaft of theactuating element and the drive shaft, the planetary gear includinga. asun gear coaxial with the rotary shaft and keyed thereto for rotationtherewith about the axis of the shafts, b. a ring gear concentricallysurrounding the sun gear, the ring gear being coaxial with the driveshaft and keyed thereto for rotation therewith about the axis, c. idlergear means meshing with the sun and ring gears and interconnecting thesame, and d. a housing carrying the idler gear means and mounted forrotation about the axis,
 2. releasable latch means arranged selectivelyto permit and stop rotation of the gearing housing,
 3. an exteriorhousing surrounding the gearing housing, and
 4. spring means connectedbetween the gearing housing and the exterior housing, the spring meansbeing biased to press the gearing housing against the latch means toprevent rotation of the gearing housing.